QQuickTableView: use QMap instead of a QRect to keep track of loaded columns

TableView keeps track of which rows and columns that are loaded
at any point by using a QRect called "loadedTable". loadedTable
basically describes the top-left and bottom-right corner of the
table that has been loaded (which also is what ends up visible
on screen).

But now that we prepare for making it possible to hide rows
and columns, using just a QRect becomes to simple. A rectangle will
only tell what the edges of the table are, but not if any of the
rows and columns in-between are hidden and therefore not loaded.
So a QRect(0, 0, 10, 10) will give us the impression that we have
10 visible columns on screen, but in reality, we might have a
lot less.

This patch will change this to instead use two QMaps to record
loaded rows and columns. This will make it much more easy
to deal with hidden rows and columns in upcoming patches. We
use a QMap instead of a QHash/QSet to keep the list of columns and
rows sorted, since we frequently still need to know the edges of
the table, like before.

Change-Id: I45736485c67042403b095e73b5f2effa411281d0
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 11 insertions, 3 deletions

diff --git a/src/quick/items/qquicktableview_p_p.h b/src/quick/items/qquicktableview_p_p.h
index 2ed04f8d29..ed6f8026a2 100644
--- a/src/quick/items/qquicktableview_p_p.h
+++ b/src/quick/items/qquicktableview_p_p.h
@@ -213,13 +213,14 @@ public:
     QVariant assignedModel = QVariant(int(0));
     QQmlComponent *assignedDelegate = nullptr;
 
-    // loadedTable describes the table cells that are currently loaded (from top left
+    // loadedRows/Columns describes the rows and columns that are currently loaded (from top left
     // row/column to bottom right row/column). loadedTableOuterRect describes the actual
-    // pixels that those cells cover, and is matched agains the viewport to determine when
+    // pixels that all the loaded delegate items cover, and is matched agains the viewport to determine when
     // we need to fill up with more rows/columns. loadedTableInnerRect describes the pixels
     // that the loaded table covers if you remove one row/column on each side of the table, and
     // is used to determine rows/columns that are no longer visible and can be unloaded.
-    QRect loadedTable;
+    QMap<int, int> loadedColumns;
+    QMap<int, int> loadedRows;
     QRectF loadedTableOuterRect;
     QRectF loadedTableInnerRect;
 
@@ -283,6 +284,11 @@ public:
     qreal resolveColumnWidth(int column);
     qreal resolveRowHeight(int row);
 
+    inline int topRow() const { return loadedRows.firstKey(); }
+    inline int bottomRow() const { return loadedRows.lastKey(); }
+    inline int leftColumn() const { return loadedColumns.firstKey(); }
+    inline int rightColumn() const { return loadedColumns.lastKey(); }
+
     void relayoutTable();
     void relayoutTableItems();
 
@@ -299,6 +305,8 @@ public:
     void syncLoadedTableRectFromLoadedTable();
     void syncLoadedTableFromLoadRequest();
 
+    int nextVisibleEdgeIndexAroundLoadedTable(Qt::Edge edge);
+
     bool canLoadTableEdge(Qt::Edge tableEdge, const QRectF fillRect) const;
     bool canUnloadTableEdge(Qt::Edge tableEdge, const QRectF fillRect) const;
     Qt::Edge nextEdgeToLoad(const QRectF rect);